In this broad context, my main current interests lie in exploring the phenomenology of Dark Matter models,
particularly via indirect detection methods (gamma rays, charged cosmic
rays, neutrinos) and with a special attention to our recent proposal of
Minimal Dark Matter, and in Neutrino Cosmology.

~~~

In the following, I briefly
review my past research activity in some
detail, and give an outlook of the open projects and directions.

I began my work in Particle
Theory Beyond the SM by computing some
relevant observables in the framework of the theory proposed by R.
Barbieri, L. Hall and
Y.
Nomura (Phys.Rev.D63:105007,2001), an extension of
the
Standard
Model to five dimensions
endowed with a
supersymmetric
structure. The theory is successful in
providing a description of the mechanism of
electroweak symmetry breaking thanks to the extra dimension, while
ensuring calculability for several quantities, a property that is not
so common among extra dimensional models. In
collaboration
with G. Cacciapaglia and G. Cristadoro, in [1] I found
that the production
rate of the Higgs boson via gluon fusion
(which
is the main channel at a hadron collider) is significantly suppressed,
due
to cancellations among the additional (Kaluza-Klein) states of the
theory.In [2] we
showed
that the theory is compatible with the precision measurements of muon
anomalous magnetic moment,
by explicitly computing all the relevant
additional
contributions to such a quantity and finding them small.

In [4], in
collaboration
with A. Romanino, Y. Lin and G. Cacciapaglia, I shifted to a more
general
class of models, characterized by large
flat extra dimension accessible
to
a sterile neutrino. We analysed the effects in
the context of supernova
physics,
where
resonant oscillations between the Standard Model electron neutrino and
the
additional sterile states provide an unconventional escape channel. We showed (via numerical and
analytical work) how previous bounds can
be
largely overcome, thanks to a feedback mechanism that self-limits the
energy
loss, and we discussed positive effects towards supernova explosion.

In [5] we
completed the
previous analysis including the effects of muon and tau neutrinos
escape,
showing how a feedback prevents an unacceptable energy loss also in
this
case. For all the different scenarios, we discussed the
signatures
in the neutrino signal on Earth.

In [7] we performed a
thorough analysis of oscillation signals generated by one extra
sterile neutrino,
extending previous analyses done in simple limiting cases and including
the effects of established oscillations among active neutrinos. Many
New Physics candidates act effectively as sterile neutrinos, so that we
include them all. We consider as probes the
solar, atmospheric, reactor and beam
neutrinos, Big-Bang Nucleosynthesis (He4, D), the Cosmic Microwave
Background, Large Scale Structure,
supernovae and neutrinos from other
astrophysical sources. We found no evidence for a sterile neutrino in
present data, we identified the still allowed regions, and studied
which future experiments can best probe them: sub-MeV solar
experiments, more precise studies of CMB or BBN, future supernova
explosions... I particularly was involved in the SN and cosmological
studies.

In [9], we addressed
the implications on solar neutrino
oscillations of the
recent proposal that the mass of the
neutrinos and the field responsible for dark energy may be connected,
leading to the effect of mass varying
neutrinos depending
on environment. We stressed the model
independent consequences, finding in particular that a connection
between the effective Delta m^2 in the Sun and the absolute neutrino
mass scale is established in these scenarios. This leads to the
possibility of explicitly testing the model and to other interesting
consequences both for the neutrinos and for the mechanism of dark
energy.

In [10] we presented
results on neutrino fluxes from the annihilation
of Dark Matter particles accumulated in the center of the
Earth
and the Sun. They will be hopefully detected in the Neutrino Telescopes
(Antares, IceCube, a large Cerenkov detector...). The neutrino fluxes
carry precious information on the main properties of DM (its abundance,
its mass and its annihilation branching ratios), opening unique windows
on its nature and on the theory that encompasses it.We computed precisely the
expected neutrino yield and, especially, the
neutrino spectra, which are more free from astrophysical uncertainties.
We develop the appropriate formalism to follow the neutrino production,
the evolution of the fluxes in the matter of the Earth and the Sun
(determined by flavor oscillations, absorptions/scatterings and tau
regeneration) and in the vacuum and finally the detection signatures.

In [11] we explored a
new approach to the Dark Matter problem: while Beyond-the-SM theories
often provide DM candidates with an obscure phenomenology and an ad-hoc
method for stabilization (such as R-parity in SuSy), we looked for a
viable candidate just adding to the SM a multiplet in some
representation of SU_L(2) x U_Y(1).We find that a quintuplet
with zero hypercharge provides a new minimal
candidate for Dark Matter
that is fully successful: weakly interacting, electrically neutral and
(most importantly) automatically stable on cosmological time scales. We
computed its distinctive phenomenology at colliders (the LHC) and in
experiments of direct and indirect DM detection, finding that the
particle can be detected in the next generation of experiments.

In [12] we investigate
the cosmology of ordinary neutrinos
and of possible extra light particles. We make use of the most
recent data from Cosmic Microwave
Background, Supernovae type Ia, Large Scale Structure, Lyman-alpha
forest, Baryon Acoustic Oscillation peaks etc. We obtain
stringent constraints on the neutrino mass, the effective neutrino
density and the properties of proposed new interacting light particles
that diminish the neutrino free-streaming. It should be noted that we
performed all the analysis making use of numerical codes and tools
written and developed by ourselves instead of the commonly used
CMBfast-derived tools.

With [13] we investigated
how unconventional cosmologies can relax the stringent bounds on
sterile neutrinos. We open the way to a possible primordial leptonic asymmetry, that
has the effect of suppressing the production of sterile neutrinos in
the Early Universe, therefore modifying the constraints from BBN and
from LSS. We identify the portions of the parameter space that can be
reopened by introducing a given asymmetry. In the case of the LSND
sterile neutrino, we find that a primordial asymmetry of the order of
10e-4 is needed in order to lift the conflicts with cosmology.

With [14] we revisited the computation of the cosmological relic abundance in the Minimal Dark Matter proposal introduced in [11], including non-perturbative 'Sommerfeld' corrections.
These were found to have a very relevant effect in enhancing the DM
annihilations. We also study the peculiar behavior of the DM particles
while crossing the Earth at Ultra High Energies, in order to assess the
possible detectability in future cosmic ray and neutrino telescopes
(e.g. Icecube, Auger, Antares).

In [15] we precisely calculated the indirect detection signatures of the Minimal Dark Matter model of [11].
We computed the fluxes of positrons, antiprotons and gamma rays from
the annihilations of DM particles in the galactic halo and their
propagation in the galaxy (designing our own computational tools). We
found distinctive and univocal predictions (the model has no free
parameters). The enhancement in the annihilation cross section
discussed in [14] put the foreseen fluxes within the reach of those that were upcoming experiments, PAMELA in particular.

When the PAMELA satellite announced preliminary data on the positron flux, showing confirmation for an excess over the expected background that previous experiments had already exposed, we compared in [16] the fluxes from Minimal DM annihilations predicted in [15]
with such data. We found a remarkably good agreement, and we were able
to determine the set of astrophysical parameters that gives the best
fit. Later, we summarized in [19] the status of the model.

In a subsequent paper [17], we performed a model independent analysis of the PAMELA preliminary data on positrons and anti-protons, together with less known but relevant data from cosmic ray balloon experiments
(ATIC and PPB-BETS). We looked for which DM models can explain the
signals that appear in the data while remaining compatible with the
searches in all other channels. We find that the PAMELA results alone,
if due to DM annihilations, individuate a quite unusual DM particle:
either very heavy (above 10 TeV) or lighter but annihilating mainly
into leptonic channels such as DM DM --> e+ e-. Adding the balloon
datasets, only the second possibility is favored.

In [18] we pursued the model independent analysis of multi-messenger indirect signatures
extending to gamma rays and synchrotron radiation from the galactic
center and dwarf satellite galaxies. We found that these observations
impose stringent constraints: a tension is present with the explanation
of the PAMELA and ATIC data in terms of DM annihilations, unless the DM
halo profile is significantly more smooth than expected from numerical
simulations.

In [20] we considered another interesting possible signal of DM indirect detection: fluxes of anti-deuterium
synthetized in galactic annihilations. We focussed on the `very heavy
Dark Matter' scenarios individuated by the recent data, and we found
promising perspectives especially for primary annihilation channels
into quarks.

Another relevant test of the Dark Matter invoked to explain the positron excess in PAMELA is the flux of gamma rays produced by inverse Compton scattering
of such energetic positrons on low energy ambient photons in the
galactic halo. This signal has the advantage of being less sensitive to
astrophysical details than the gamma rays from the Galactic Center
discussed above. We computed this flux for several cases and for a
range of DM models in [21], finding again stringent constraints.

In [22]
we looked once again at the implications of Dark Matter annihilations,
this time on the cosmological evolution of the universe. Indeed, the
annihilations of Dark Matter during the epoch of galaxy formation
inject charged particles and energy, producing reionization and heating of the primordial gas.
Comparing with the observed optical depth (from CMB) and the measured
temperature of the intergalactic gas we found relevant constraints on
DM properties, in the particular for the PAMELA-motivated models. We
also found general constraints for more `ordinary' Dark Matter.

When the Fermi satellite started releasing data on diffuse gamma ray, we updated the constraints formerly obtained in [21] to take the new measurements into account ([23]), at the same time improving and enlarging the analysis (e.g. to the case of decaying DM).

In [25] we took a close look at a class of DM models often advertised as able to explain the cosmic ray excesses, namely models with multistate DM
coupled to light hidden sector bosons. With a detailed calculation, we
showed instead that such models suffer from several tensions with the
gamma ray constraints and in reproducing the cosmological abundance of
DM. They are therefore only very marginally viable.

Ref. [26] represents the coronation of a long effort directed to produce `ingredients' and `recipes' for DM indirect detection,
using state of the art calculations and in a consistent framework and
provide this to the community for easy use. We computed the energy
spectra of e+-, anti-p, anti-d, gamma rays, nu and anti-nu e, mu and tau
from DM annihilations or decay in the Galaxy; the propagation functions
for charged particles in the halo; the energy spectra of charged
particles at the location of the Earth; the gamma ray fluxes from
Inverse Compton scattering in the galactic halo and finally the spectra
of extragalactic gamma rays. The concrete goal is that now the community
has at disposal a suite of results which can make it easier to assess
which DM models can explain possible signals that might appear in the
data (e.g. the current PAMELA excess in positron fluxes, or future
possible results from the Fermi telescope in gamma rays...) while
remaining compatible with the searches in other channels, or producing
predictions for other channels, in a full multi-messenger approach.

In Ref. [27] and [28] I participated in two analyses of the impact of ElectroWeak corrections
(i.e. the emission of weak bosons) on the annihilation of DM particles.
The process is important, because it can lift the suppression which
naturally depresses the cross section of Majorana DM particles
annihilating into light fermions (known as helicity suppression),
leading to very different resulting spectra.

In Ref. [29] I worked on the phenomenology of the so-called Asymmetric Dark Matter
(aDM) scenario, which assumes the existence of a primordial asymmetry
in the dark sector. We studied in particular the effect of oscillations
between dark matter and its antiparticle on the re-equilibration
of the initial asymmetry before freeze-out, which enable efficient
annihilations to recouple. We calculated the evolution of the DM relic
abundance and showed how oscillations re-open the parameter space of aDM
models, in particular in the direction of allowing large (WIMP-scale)
DM masses.

In Ref. [32] we derived new bounds on decaying Dark Matter
from the gamma ray measurements of (i) the isotropic residual
(extragalactic) background by the FERMI satellite and (ii) the Fornax
galaxy cluster by the HESS telescope.
We found that those from (i) are among the most stringent constraints
currently available, for a large range of DM masses and a variety of
decay modes, excluding half-lives up to ~10^26 to few 10^27 seconds. In
particular, they rule out the interpretation in terms of decaying DM of
the e+- spectral features in PAMELA, FERMI and HESS, unless very
conservative choices are adopted.

In Ref. [33] and [34] we derive constraints on the DM annihilation cross section from the antiproton measurements
performed by PAMELA, finding that thay can be competitive with the
gamma ray ones. In [33]
we then apply them to specific SuSy models in order to constrain also
an `internal' property of the models: the mass splitting between
charginos and neutralinos. In [34]
we assess also the sensitivity of the upcoming AMS experiment and its
ability to reconstruct DM properties from a possible signal.

With [35] I moved to the phenomenology of DM direct detection: we discuss a powerful framework (based on non-relativistic operators)
and provide a self-contained set of numerical tools to derive the
bounds from some current experiments on virtually any arbitrary model of
Dark Matter.

In Ref. [36], we address the often-neglected role of bremsstrahlung
processes on the interstellar gas in computing indirect signatures of
Dark Matter (DM) annihilation in the Galaxy, particularly for light DM
candidates in the phenomenologically interesting O(10) GeV mass range.
We find that the effects of bremsstrahlung are important, or even
dominant, in determining the gamma-ray spectrum from DM.
Ref. [37] represents a significant upgrade of Ref. [10], in particular with the improved knowledge provided by Ref. [26]: we computed the spectra of neutrinos from DM annihilations in the Sun
including electroweak correction, state of the art energy losses in
solar matter (computed with GEANT) and secondary neutrinos.

In Ref. [38] we explored the possible yield of anti-Helium nuclei from galactic DM annihilations (in analogy with the work in Ref. [20]
on antideuterium: while in principle the prospect are good since the
astrophysical background is very suppressed at the interesting energies,
we find that only for very optimistic configurations it might be
possible to achieve detection with current generation detectors.

Since 2010 another anomaly has attracted a lot of attention in the community: a GeV diffuse excess from the Galactic Center region,
which can be explained in terms of DM with a mass of tens of GeV
annihilating in quarks or leptons with thermal annihilation cross
section. In Ref. [39] we
investigated the antiproton constraints on such an explanation. We
treated with particular care the uncertainties related to the
propagation of antiprotons in the Galaxy and in the proximity of the
solar system (the so-called solar modulation effects). We found that,
while the DM interpretation is ruled out for stringent assumptions, in
the full case (thin propagation halos and/or a conservative treatment of
solar modulation) no firm conclusion can be reached.

Ref. [40] approached a rather different topic: we considered an electroweak triplet
as an extension of the Standard Model (a good DM candidate, if the B-L
symmetry is enforced) and perform an analysis of the reach for such a
particle at the high-luminosity LHC and at a futuristic 100 TeV pp collider.
We do so for the monojet, monophoton, vector boson fusion and
disappearing tracks channels. For the large mass region, high energy and
high luminosity conditions will be necessary.

In ref. [41] and ref. [42] I went back again to antiprotons. First we revisited the computation of the astrophysical background and of the DM antiproton fluxes
fully including some effects which are often considered subleading but
actually prove to be quite relevant: diffusive reacceleration, energy
losses (including tertiary component) and solar modulation. Then, as
soon as the data from AMS-02 came out, in [42]
we reevaluated again the secondary astrophysical antiproton to proton
ratio and its uncertainties, finding that there is no unambiguous
evidence for a significant excess with respect to expectations, and we
provided a first assessment of the updated Dark Matter constraints.

Ref. [43] constitutes an upgrade and complement of [26], the collection of tools and recipes for DM indirect detection. We here focussed on secondary radiation: bremsstrahlung and Inverse Compton gamma rays and synchrotron radiation.

Ref. [44] we reconsider the model of Minimal Dark Matter, almost ten years after we proposed it in [11], and compute its updated gamma ray signatures.
We find that the model is constrained by the line searches from the
Galactic Center: it is ruled out if the Milky Way possesses a cuspy
profile such as NFW but it is still allowed if it has a cored one. We
also explore a wider mass range, which applies to the case in which the
relic abundance requirement is relaxed.

The work in ref. [46] derives bounds on annihilating or decaying Dark Matter from yet another aspect: the synchrotron radiation constrained by the radio surveys of the Galaxy. We employed the tools developed in [43]
and we compared with standard and new surveys (such as e.g. those by
the CMB satellite Planck). The derived bounds turn out to be not very
stringent, but complementary to those obtained with other indirect
detection methods, especially for dark matter annihilating into leptonic
channels.

~~

During my laurea thesis
work I also dealt with the physics of Strong Interactions and Quantum
Chromodynamics, under
the supervision of P. Nason and G.
Marchesini. We derived a formula for a
particular regime in Drell-Yan
processes
(the production of a lepton--antilepton pair in proton--antiproton
collisions). Namely, the intersection of
threshold production and small transverse
momentum regimes. I had the opportunity of
studying in a certain detail the resummation
of soft gluon emissions.